If McConnell & the GOP simply held hearings for Garland then rejected him on an up-or-down vote, they wouldn't be subject to hypocrisy charges now.

Why did they bother creating a principle - no nominees in an election year - that they would so quickly abandon?

Here's why...

...Garland's nomination was a nod to the Republican majority. He was long promoted by Orrin Hatch. He was 64 and widely seen as moderate. He would have created an ideologically balanced Court.

To give Garland the platform of hearings would emphasize all that to the public...

...Republicans could still vote No, but they would have to do so while fighting uphill that somehow Garland was some sort of activist judge and Obama was playing politics with the Court.

Instead of letting their long-standing narrative get undercut, they shut down the process...

...Democrats (and Republicans!) had a long history of being compromising with judges, despite all the friction. The Bork fight resulted in Kennedy, not a Democratic pick. Thomas was not filibustered. Hatch recommended Ginsburg...

...Dems fought several Bush appellate picks but compromised on some strongly conservative ones to avoid a Republican nuclear option. (Conservatives sunk Miers, not Democrats.) As Graham loves to note, he backed Obama's first two picks...

...Garland was offered in the same spirit of consensus. But as a replacement for Scalia, adjusting the ideological calibration of the Court was untenable for Republicans. So they shut it down in a way that would mask that spirit...

...This matters because the Republicans justification for abandoning their own principle is "Democrats would have done it too." They need folks to think both parties are equivalently partisan, equivalently ruthless and disinterested in compromise...

...Maybe in the near future, in response, Democrats will become equivalently ruthless. But that's not the recent history, it's not what happened in 2016, and it's not Joe Biden's record and not what he has been running on.